Misalignment or mistracking of a conveyor belt can have various adverse consequences including belt downtime, and damage to mechanical components and to the belt.
There are many factors which can cause conveyor belt misalignment. For example, misalignment can be produced by a tail roller or idler frames which are not perpendicular to the direction of belt movement. A change of length in the belt due to a bad splice, incorrect loading and so on can also cause mistracking. Other causes of belt misalignment include scrapers or skirtings which are incorrectly adjusted, material build-up on idlers, damaged lagging on rollers, and so on.
The applicant is aware of a number of techniques which have been proposed to correct belt misalignment, substantially in an automatic manner.
One proposal makes use of a central pin which is inclined at 45° to the vertical. The pin supports a belt carriage to which horizontally-orientated rollers are mounted. If the belt drifts to one side then a roller, on that side, tilts downwardly and, due to the inclination of the pin, also moves in a horizontal sense. The conveyor belt then automatically tends to move to a higher roller and a self-correcting action takes place.
In a different approach, a roller with tapered ends, of reducing size, is mounted to a central pin for limited rotational movement in a horizontal plane. Movement of the belt to one side causes the belt to contact the tapered surface on that side of the roller. This action accelerates the tapered surface which is then moved in the same direction as the direction of belt movement. The belt then tends to revert to a central position with a correcting action.
Another solution is proposed in a so-called bidirectional belt trainer which makes use of a ball joint to which a roller carriage is mounted for pivotal movement in a horizontal plane. Tracking of a belt to one side causes a corresponding movement of the roller carriage and corrective action which is generated through the medium of an intermediate control device helps to restore the belt to a desired position.
Another solution requires a carriage to be mounted to a centrally positioned pivot point. Rollers supported by the carriage are movable in unison with the carriage to correct belt misalignment.
Each of the aforementioned techniques, in the applicant's opinion, functions at least to some extent in a satisfactory manner. However, some of the systems are difficult to install or expensive to fabricate. There is also a need for a system which can be adjusted on site to suit particular installation conditions.